A need exists in many technical applications for a driving device intended to act upon a body so as to move it along a predetermined path. Often said path is mainly linear, but applications also occur where the movement takes place in a curved path (curved track). In certain cases the movement takes place at the same time as the body describes a turning, or possibly a rotational, movement at least during a part of its movement along the path. Frequently, demands are made for a rapid movement and many times it is desired that the driving device should function reliably under difficult environmental conditions where dirt and particles have a disturbing effect, such as a corrosive or abrasive effect on the driving device.
To meet the abovementioned needs it is known to use e.g. linear motors, hydraulic components (cylinders and pistons), articulated couplings, screw rods, etc.
Electromechanical devices, which usually consist of a rotating threaded spindle along which a torsionally rigid "nut" acts as a driver for the linear movement, offer only limited stroke lengths, since the spindle is merely supported at its two ends. Such devices are also easily affected when installed in environments where e.g. solid particles and dirt deposit on the threads of the spindle and in such environments said devices as a rule present unsatisfactory operational reliability.
The abovementioned technique, as a rule, is space-demanding, solves problems only within limited technical areas and demands, especially in cases of extended paths of motion, that the structures should be mechanically stable. This stability is difficult to achieve with the driving devices previously known and referred to above unless they are given larger dimensions than those demanded by the force or power actually required. Automatic drives for pneumatic and hydraulic equipment are expensive. Consequently the known techniques involve considerable costs.